The present invention relates to aspects of an invention associated with a two-pack urethane foam composition for reinforcing a closed sectional structure of the body of a vehicle, e.g., automobile, by filling a urethane foam, by injecting the two-pack urethane foam composition, into the closed sectional structure thereof.
More particularly, one aspect of the invention relates to a two-pack urethane foam composition which is composed of a two-pack of a polyol compound as a major component and a polyisocyanate compound as a curing agent, and which can form a urethane foam by foaming and curing upon injecting (applying) immediately after mixing the two components at ambient temperature. On the other hand, other aspects of the invention relate to an injection method for injecting the two-pack urethane foam composition, a cured urethane foam-filled vehicle body member having an opening for confirming the injecting and filling of the two-pack urethane foam composition, a cured urethane foam-filling confirming method for confirming the appropriateness of a filling volume of the two-pack urethane foam composition, and a two-pack urethane foam composition injecting apparatus and method capable of automatically injecting and filling the two-pack urethane foam composition into the closed sectional structure of the vehicle body.
In recent years, the automobile industry has been required to ensure the rigidity of an entire vehicle body for increasing the safety of automobiles and improving a soundproof property of a riding space. In order to achieve these requirements, demands have be made to provide the intensity and the rigidity and the soundproof property to a portion where a variety of loads such as impact and so on are imposed, such as a center pillar having a closed sectional structure, a front pillar of a vehicle body having a closed sectional structure and so on. Moreover, in order to protect riders from impact, a crushable zone has to be provided on each of the front and rear sides of the vehicle body and a solid safety cell has to be configured for a cabin where the riders are seated in order to ensure a riding space for the riders.
On the other hand, problems may arise in that the weight of the vehicle body is increased and the fuel economy becomes poorer if a thick panel is used as each of the pillar, chassis or the like having a closed sectional structure in order to improve the rigidity and the soundproof property of the cabin.
Therefore, it has been suggested to develop structures and methods for increasing the rigidity of the vehicle body while keeping the thick panel of the pillar of the vehicle body and so on thin, for instance, by injecting and filling a cured urethane foam into the closed sectional structure of the pillar thereof and so on by using the above two-pack urethane foam composition. In combination of development of making the vehicle body lightweight, it has also been considered to inject and fill a urethane foam into a closed sectional structure of a roof portion or a locker portion or the like, in addition to the pillar and so on.
Various problems, however, may result in injecting the two-pack urethane foam composition into the closed sectional structure.
For instance, when the two-pack urethane foam composition is injected in a fluid state, there are occasions that the injected composition leaks outside or expands from the injection port due to a back flow. The injected composition leaks or expands even from a small gap of the closed sectional structure so that there is the risk that the appearance of the automobile may be impaired (hereinafter referred to as the first problem).
It has now been found by the present inventors that the two-pack urethane foam composition does not leak or expand from small gaps in an injecting portion, if any, due to becoming cured to an appropriate level of viscosity immediately after injection by limiting foaming characteristics of the two-pack urethane foam composition, particularly a cream time and a rise time, as well as adjusting the specific gravity of the filed urethane foam to become 0.6 to 0.01 by adjusting the amount of the foaming agent.
When such a two-pack urethane foam composition of a curable type having a high reactivity at ambient temperature (0° C.-50° C.) is used, it has been found to raise a practically significant problem that, when it is discharged or injected from a conventional two-pack mixing apparatus, there are occasions in which the two-pack urethane foam composition cures in the mixing apparatus during injecting on site, and thus clogs the mixing apparatus during the injecting process (hereinafter referred to as the second problem).
It is designed as a matter of course to inject a predetermined amount of the two-pack urethane foam composition, corresponding to the volume of the closed sectional structure to be injected and filled with the composition, with a foaming rate and other foaming conditions of the two-pack urethane foam composition taken into account. If an unpredictable problem would occur with an injecting apparatus or the like; however, there may result an unpredictable occasion that the filling volume of the cured urethane foam becomes less than the desired range and a hollow portion may result, thereby making it difficult to reach the designed rigidity. It is considered that the lack of the filling volume may also arise due to accidental damage of a partition plate disposed in the closed sectional structure.
In actual cases, however, the present situation resides in that there is no manner of preventing the lack of such filling volume of the urethane foam in advance, and that the appropriateness or inappropriateness of the filling volume can be judged for the first time by carrying out impact tests or by measuring the rigidity of an actual car or analyzing the vibration thereof after the production line. Therefore, the problem is that the design intensity and rigidity of the automobile cannot be ensured during the production line (hereinafter referred to as the third problem).
Furthermore, in general, the production of automobiles is carried out by mass production by the transfer and assembly method using a belt conveyor on the basis of the division of work. In order to adapt a production line to such a mass production, however, it is required to develop an injecting apparatus and an injecting method for injecting and filling a two-pack urethane foam composition into the closed sectional structure of the vehicle body (hereinafter referred to as the fourth problem).